unifdef: Fix case where a multiline comment follows a directive.

Sponsored by:	Klara, Inc.
Reviewed by:	kevans
Differential Revision:	https://reviews.freebsd.org/D41026

usr.bin/unifdef/tests/Makefile

@@ -2,6 +2,7 @@
 
 PACKAGE=	tests
 
+ATF_TESTS_SH=	unifdef_test
 NETBSD_ATF_TESTS_SH=	basic_test
 
 ${PACKAGE}FILES+=	d_basic.in

usr.bin/unifdef/tests/unifdef_test.sh

@@ -0,0 +1,22 @@
+#
+# Copyright (c) 2023 Klara, Inc.
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+
+atf_test_case hash_comment
+hash_comment_head() {
+	atf_set descr "multiline comment follows directive"
+}
+hash_comment_body() {
+	cat >f <<EOF
+#if FOO
+#endif /*
+*/
+EOF
+	atf_check -o file:f unifdef <f
+}
+
+atf_init_test_cases() {
+	atf_add_test_case hash_comment
+}

usr.bin/unifdef/unifdef.c

@@ -886,8 +886,9 @@ parseline(void)
 			retval = LT_ELIF;
 	}
 	/* the following can happen if the last line of the file lacks a
-	   newline or if there is too much whitespace in a directive */
-	if (linestate == LS_HASH) {
+	   newline or if there is too much whitespace in a directive,
+	   or if a directive is followed by a multiline comment */
+	if (linestate == LS_HASH && !incomment) {
 		long len = cp - tline;
 		if (fgets(tline + len, MAXLINE - len, input) == NULL) {
 			if (ferror(input))